1. Field of the Invention
This invention relates generally to backflow check valves for use with liquid flow and administration apparatus for medical purposes.
2. Description of the Prior Art
A common problem of known devices of the conventional type is that upon reversal of liquid flow through tubing from a hypodermic syringe or the like, the known type check valves fail to respond as quickly as desired to the closed position. That is, there is always the risk of backflow from the output to the input, which in many instances is very undesirable, and in some cases, even deadly.
There have been devices made to be normally closed and under stress, whereby the valve in order to remain open must be subject to a high flow pressure, and thus when the flow pressure is decreased, the valve will quickly close. This is a great improvement over the afore-mentioned check valve; however, it still can be improved upon. The disadvantage of this type is that the valve disc itself may tend to move off center and thus have a tendency to bind an edge against one of the peripheries of the enclosing wall.
Other devices comprising one-way valves that are normally in the closed position fail to permit injection and aspiration when attached to a syringe.
Existing prior art patents which may be pertinent to the present invention are as follows:
______________________________________ Raines U. S. Pat. No. 4,535,820 8/20/85 Mackal, et al. U. S. Pat. No. 3,831,629 8/27/74 Steer, et al. U. S. Pat. No. 3,570,484 3/16/71 Harautuneian U. S. Pat. No. 3,385,301 5/28/68 De See U. S. Pat. No. 3,192,949 7/6/65 ______________________________________
U.S. Pat. No. 4,535,820 was invented by the same inventor as the present invention, and assigned to the same assignee as the present application. However, in this device the valve is normally closed and does not have structure therewith for permitting quick and easy injection and aspiration of fluids when the device is attached to a syringe. The purpose of the present invention is to overcome this.
The Mackal, et al. device (U.S. Pat. No. 3,831,629) is for a two-piece check valve having a reciprocable valve element. A liquid-injecting syringe can be used with this device.
U.S. Pat. No. 3,570,484 to Steer is a device for administering intravenous injections of liquids. A valve body has a non-return valve therein together with a plunger which when depressed will open the valve. However, the structure of this device is quite a bit different from that of the present invention.
U.S. Pat. Nos. 3,385,301 and 3,192,949 disclose valve elements which can be opened by insertion of a syringe 50 and 36 into the respective devices.
None of the known prior art devices offer the new and novel features of the present invention.